The present invention relates to an optical disk recording/reproducing apparatus and also a seek control method thereof, for enabling to record and reproduce information onto/from an optical disk having a land and a groove formed on recording surface thereof, and in particular, it relates to an optical disk recording/reproducing apparatus and a seek control method thereof, for enabling a seek operation of moving an optical spot in a radial direction of the disk towards to a track desired.
An optical disk, such as, CD or DVD, etc., for example, representatively, is widely used, as an information recording medium of non-contact, a large memory capacity and a low cost, and also of enabling data access at high speed, in particular, for the purpose of recording/reproducing digital audio data and/or digital video data, and further as a data recording medium for use in a personal computer. In particular, in recent years, so-called a re-writable optical disk is also used widely, such as, DVD-RAM (Digital Versatile Disc of Random Access Memory Type), for example.
Within an optical disk recording/reproducing apparatus for conducting recording or reproducing onto/from such the optical information medium, an acceleration pulse is generated for moving an optical spot from an optical pickup into the radial direction of the disk, in other words, crossing or traversing tracks towards an objective or target track, when changing the track to be conducted recording or reproducing thereon/from, thereby moving an optical pickup including an objective lens therein; i.e., so-called a seek control. However, in general, such the seek control is composed of the following three (3) stages: i.e., an acceleration stage of applying the acceleration pulse onto a driving mechanism of the optical pickup; a constant speed stage of keeping moving velocity of the optical pickup at a desired value; and further a deceleration stage of applying a deceleration pulse so that the moving velocity of the optical pickup comes down to be near to zero (0) at the target track. And, after completing of the seek control, a track following control is carried out, again, for bringing the optical spot of the optical pickup to follow the track, through a tracking servo system, within the optical disk recording/reproducing apparatus, and thereby conducting recording/reproducing on the target track.
By the way, for the purpose of executing a drawing or pulling operation onto the target track in short time and with stability under such the seek control, a method for controlling the moving velocity of the objective lens within a desired limit or range, when moving the seek control into a tracking control, is already disclosed, for example, in the following Patent Document 1, through compensation upon a peak value of the deceleration pulse to be applied within the deceleration stage, or pulse width thereof, upon basis of a tracking error signal during when the deceleration pulse is outputted.
On the other hand, in recent years, accompanying with an increase of recording capacity of the optical disk, as such the optical information recording medium mentioned above, also the recording density thereof becomes high in the density. Thus, narrowing is made on a pitch between the recording tracks, and for example, on a re-writable type optical disk, such as, DVD-RAM, not only a groove, but also a land is formed, spirally, between the grooves, and a single track format is adopted, i.e., the land and the groove appear alternately per one (1) rotation. On the recording track defined along those lands and grooves is recorded or reproduced the information.
Then, in the following Patent Document 2, for example, is already known a seek control method for inhibiting the generation of an overshoot, etc., so as to narrow the pitch between the recording tracks, by taking ill influences into the consideration, which are caused due to time delay in detection when generating a track traversing pulse up to control of the optical spot, which is conducted at the timing of a sampling clock, thereby achieving a stable pulling operation into the tracking control.
Further, for example, in the following Patent Document 3 is already known a tracking control apparatus and a method thereof, wherein detection is made on the movement of a beam spot into the disk radial direction from a phase relationship between a tracking signal and a signal, which is obtained through digitizing an amplitude detection signal produced by a reflection light, and control is made on a brake in moving direction of the beam spot, when detecting that the beam spot crosses the track at the scanning position thereof, after change from the seek operation into the tracking operation, thereby achieving a stable pulling operation and a high-speed of the tracking.
[Patent Document 1] Japanese Patent Laying-Open No. Hei 09-102135 (1997);
[Patent Document 2] Japanese Patent Laying-Open No. 2005-285216 (2005); and
[Patent Document 3] Japanese Patent Laying-Open No. 2001-202635 (2001).
However, with such the conventional arts as mentioned above, in particular, the methods and the apparatuses described in the Patent Documents 1 and 2, the correction or compensation is made upon the peak value and/or the pulse width in a series of deceleration pulses, or upon the deceleration pulse for the time delay in detection thereof; however, any one of those takes the timing for starting the pulling operation into the tracking servo control under the tracking serve system into the consideration thereof. Further, in case when recording or reproducing information along those lands and grooves, which are formed spirally on the recording surface, such as, DVD-RAM, for example, the difference is very important, that the desired track, onto which the optical spot should be moved, is the groove or the land, for the seek operation of moving the optical spot into the radial direction on the optical disk, including an operation shifting into the tracking servo thereafter. Nor sufficient consideration is paid for the timing for switching from the seek operation into the tracking operation, within the tracking control apparatus and the method thereof, which are described in the Patent Document 3 mentioned above.
Thus, in particular, on the information recording medium, forming the lands and grooves spirally on the recording surface thereof, such as DVD-RAM, for example, the condition for brining the tracking error signal to be stable differs from, during the tracking operation thereafter, depending on the fact that the tracking servo is taken onto the land or the groove when conducting the pulling operation within the seek operation.
Then, according to the present invention, accomplished by taking the drawbacks of the conventional arts mentioned above into the consideration thereof, i.e., an object thereof is to provide a seek control method for enabling the pulling into the tracking servo, stably in the timing thereof, in particular, within the seek operation for moving an optical beam onto the target track traversing the tracks, in spite of the difference that the target track is the land or the groove, and further to provide an optical disk recording/reproducing apparatus enabling the seek operation, at high-speed and with stability, while adapting such the method therein.